The present invention relates to a tire/wheel assembly which enables run-flat traveling and to a run-flat support member which is employed in the tire/wheel assembly. More specifically, the present invention relates to a tire/wheel assembly and a run-flat support member which achieves both workability of tire-to-rim fit and durability for run-flat traveling.
To meet the demand from the market, numerous techniques have been proposed to enable a certain degree of emergency driving even when a pneumatic tire is punctured while driving a vehicle. Among those numerous proposals, the techniques proposed in Japanese Patent Laid-Open Publication No. 10-297226 and Published Japanese Translation of a PCT Application No. 2001-519279 enable run-flat traveling by fitting a core to a rim in a cavity of a pneumatic tire assembled to the rim and supporting a flat tire with the core.
The foregoing run-flat core has an open-leg-structured circular shell including a support surface thereof extended toward the periphery of the tire and leg portions along each side of the support surface. The run-flat core is constituted by attaching elastic rings to both of these leg portions so that the core is supported on the rim through the elastic rings. The advantage of the run-flat core is that the available rims and wheels in the market can be used as their own, without any particular modifications. Thus, the core can be accepted to the market without causing difficulties therein.
Nevertheless, the elastic rings of the core are required to be capable of supporting a load in a shell radial direction during run-flat traveling. At the same time, the elastic rings are required to be deformable in a shell axial direction when fitting to a rim or to have a low resistance to that bending deformation. To satisfy the characteristics, providing slits which extend in the shell axial direction in the elastic rings has been proposed. However, since these slits cause an infinitesimal deformation in the shell radial direction in the elastic rings, the slits are a main factor of durability degradation for run-flat traveling. In addition, there has been another problem that durability for run-flat traveling is prone to be degraded when stresses are concentrated on the elastic rings which support the circular shell.